U.S. Pat. No. 4,119,120 describes a fluid switch useful as a sampling device in chromatography systems for switching gaseous or liquid fluid streams between two possible channels. The switch can be employed in two modes. The first as a substitute for two position slider block valves used previously in the art and in the second as a plurality of interconnected switching pairs to provide a plurality of switching actions from a single control fluid switched source.
The aforesaid fluid switch comprises a series of paired enclosures formed by two depressions in a first plate, each depression having an inlet and an outlet and an elastomeric diaphragm covering the depressions. The diaphragm is held in place by a second plate having a first control inlet opposite one depression and a second control inlet opposite one depression and a second control inlet opposite the other depression. A fluid to be switched is connected into the inlets of the first plate in common. By alternatively applying a control fluid to one control inlet and then the other of the second plate, the fluid to be switched is switched from one inlet to the other by the diaphragm alternatively being deformed into one depression and then the other by the control fluid so as to seal the inlet and outlet and thereby block the flow of fluid therethrough from the inlet. Thus, the paired switch valves operate in series and when arranged in multiple arrays flow can be directed to one or the other chambers in each pair but won't proceed from one pair to any other.
A similar multiport flexible diaphragm controlled fluid switching valve is described in Italian Pat. No. 603,986, issued Apr. 27, 1960. As was the case with the valve disclosed in U.S. Pat. No. 4,119,120 and discussed above the paired switch valves are linked in series and when any one valve inlet and outlet are closed, by operation of the control diaphragm then flow of fluid is not possible to other switch valve pairs. Additionally, the inlet and outlet channels are bored within the internal portion of the support plate and thus do not provide a low dead volume passage between the valve chambers.
Other flexible diaphragm controlled fluid valve systems are taught in British Pat. No. 977,364, published Dec. 9, 1964; U.S. Pat. No. 3,095,746, issued July 2, 1963 and U.S. Pat. No. 3,057,594, issued Oct. 9, 1962.